Voltage regulation



H. c. GRANT, JR 2,076,499

VOLTAGE REGULATION April 6, 1937.

Filed Sept. 1, 1935 3 Sheets-Sheet l INVENTOR X/MLW C1, a

ATTORNEY April 1937- H. c. GRANT, JR 2,076,499

VOLTAGE REGULAT ION Filed Sept. 1, 1933 5 Sheets-Sheet 2 ENTOR INV HarryC'g mfibe/l Gra/mJI:

ATTQRNEY April 6, 1937. H. c. GRANT, JR

VOLTAGE REGULATION Filed Sept. 1, 1953 25 Sheets-Sheet 3 INVENTOR Haw/yC'am bbd/ G'rant J'.

' ATTORNEY Patented Apr. 6, 1937 UNITED STATES PATENT OFFICE 2,016,499vom'acn REGULATION Application September 1, 1933, Serial No. 687,835

19 Claims.

The present invention relates to electrical arrangements for controllingthe voltage of current from a source of electric potential subject tofluctuations in voltage, whereby the fluctuations in voltage at thesource will not be impressed across apparatus to be operated by suchcurrent.

There are many instances where a constant voltage is necessary for theoperation of mechanlsm, such as fire detecting apparatus, smokedetecting apparatus, etc. yet the location of the apparatus frequentlyis such that a current supply of this character is not available. Thus,by way of example, in the use aboard ship, where wide variations in thevoltage of the source of electric potential are known to be a commonoccurrence, of smoke detecting apparatus of the type employing a sourceof light directed upon a light-sensitive element with a current of airflowing along the path of the beam of light directed from the source oflight upon the light-sensitive element and in which the presence ofsmoke in the current of air acts to decrease the intensity of the lightfalling upon the light-sensitive element and to thereby cause an alarmsignal to be rendered, it has been found that if the light-sensitiveelement circuit has been adjusted to give detection for a reasonablylight smoke density, it will also give false alarms for a drop in theline voltage as little as four volts, it being understood that a drop inthe line voltage will cause a decrease in the intensity of the lightemitted by the source of light. For this reason a well designed smokedetecting apparatus of the type referred to requires a voltage regulatorto be used on the source of light to prevent fluctuations in the voltageapplied thereto regardless of the changes in voltage at the source ofelectric potential.

It is accordingly the principal object of the present invention toprovide means for controlling the voltage of current from a source ofelectric potential to maintain a constant value thereof across desiredterminals, in spite of relatively great variations of the voltage at thesource.

It is also an object of the invention to provide a constant voltageacross desired terminals despite not only variations of the voltage atthe source of electric potential but also variations in the load appliedacross the aforesaid terminals.

It is a further object of the invention to provide signalling means toindicate when the variations in the voltage at the source are so greatthat the apparatus of the present invention will not bring the loadvoltage back to normal, so that proper steps may be taken at once tocorrect the voltage directly at the source.

These, and other objects of the invention not specifically enumeratedabove, will be apparent as the invention is described in greater detailin connection with the accompanying drawings, where- Figure l is aconventional view showing the electrical circuits and connections of acomplete voltage regulating arrangement constructed in accordance withthe present invention.

Figure 2 is a conventional view showing in a somewhat more simplifiedmanner the principal elements of the voltage regulating arrangement ofFigure 1.

Figure 3 is a view similar to Figure 2 showing another arrangement ofprincipal elements.

Figure 4 is a view similar to Figure 2 showing a further arrangement ofprincipal elements.

Figure 5 is a view similar to Figure 2 showing still another arrangementof principal elements.

Figure 6 is a view similar to Figure 2 showing a still furtherarrangement of principal elements.

Figure 7 is a simplified conventional view showing an adaptation of thepresent invention to controlling the output voltage of an electricgenerator.

Figure 8 is a simplified conventional view showing an adaptation of thepresent invention to controlling the speed of an electric motor.

In order to simplify the explanation of the circult of the completevoltage regulating arrangement of Figure 1, reference will first of allbe made to the simplified showing of Figure 2, in connection with whichit should be noted that the regulator circuit is a special type ofWheatstone bridge in which, for example, two neon glow tubes are usedinstead of resistances. These are shown at G and T. These neon glowtubes have as an important characteristic the ability to automaticallychange their resistance so as to maintain the voltage constant acrosstheir terminals. Thus in the circuit shown in Figure '2, when thecurrent is flowing from e through resistance X through glow tube G to O,the voltage across glow tube G remains constant regardless of changes involtage across points 0 and 0 (within limits).

Neon glow tubes may be obtained for various voltages, but for thepurpose of the present explanation it will be assumed that the voltagemaintained by the glow tubes is in the order of 60 volts, varyingslightly for difierent tubes due to manufacturing variations. Also thevoltage at 0 will be considered the datum point of zero and all voltagesare referred to the voltage at 0.

Therefore, in Figure 2, current flows from the positive unregulated lineE through a rheostat W to point e, flowing to negative throughresistance X and glow tube G, which is paralleled by a series ofresistances Y, to 0. Current also flows from c through glow tube T,through resistance Z, to 0. Since the voltage drop across the glow tubesis 60 volts, the voltage at M will be 60 volts, while the voltage at Fwill be 60 volts less than that at e. As the unregulated voltage at Evaries, the voltage at 0 will likewise vary, and due to the constantvoltage drop across glow tube T the voltage at F will also vary the sameamount. The voltage at M, however, will remain constant regardless ofany variation of voltage E. Since the voltage at M is constant, thevoltage at any point S of the series of resistances Y will also beconstant. If it is desired to maintain a voltage at e of 90 volts, thevoltage at F will be 30 volts. Since the voltage at S is constant, anadjustment may be made to cause this voltage to be 30 volts. If agalvanometer relay G. R. is now connected between S and F, there will beno voltage difference across G. R. and the galvanometer pointer willfloat clear of its contacts. If, however, the voltage at E rises, thevoltage at 6 will also rise and the voltage at F will rise equally.Since the voltage at S remains constant, the galvanometer pointer willbe deflected against one of its contacts, which action can be employed(as will be explained in connection with Figure 1) to effect increasesor decreases in the amount of the resistance of the rheostat W incircuit. Therefore, upon the aforesaid rise in the voltage at E, theresistance W is increased and the voltage at e will decrease until thevoltage at F is 30 volts, when the galvanometer will be neutral. Whenthe voltage at F is 30 volts, the voltage at e will will be 90 volts,which is the desired regulated voltage. The reverse operation takesplace when the unregulated voltage at E decreases.

By way of example (neglecting the small voltage drop caused by the fiowof current through the galvanometer relay when unbalanced), if thevoltage at E were 110; at e, 90; at S, 30; and at F, 30; thegalvanometer would be balanced. If the unregulated voltage then became113 at E, the voltage at e would be 93 and at F, 33, the voltage at Sremaining at 30. Consequently, the change in unregulated voltage of 3volts from normal is transmitted directly to the galvanometer relay,resulting in the adjusting operation as just described.

Of course, with reference to Figure 2, the apparatus on which it isdesired to maintain a constant voltage is connected across the terminalsLi and L2.

Referring now to the circuit of the complete voltage regulatingarrangement shown in Figure 1, the same reference characters as wereemployed in connection with Figure 2 have been used wherever possible.However, the resistances A, B, C and D together comprise the series ofresistances shown in Figure 2 as Y. The unregulated voltage is appliedfrom the positive PQS. of the source of electric potential to theterminal line E and from the negative NEG. to the terminal line 0. Theregulated positive voltage is obtained from terminal line L1, thenegative line being shown at L2. When the voltage across terminals E and0 drops, galvanometer relay G. R. deflects I to the left, causing therelay I to operate through a circuit from negative terminal line 0,through resistance 2, through the now closed contact 3, through therelay I, through the normally closed contact 4, and through wires 5, 6and 1 to the positive terminal line E, causing the relay I to operate.The operation of the relay I closes the contact 8, permitting a currentto flow from the positive terminal line E, through wires 1, 6 and 9,through contact 8, through armature I0, through wires II and I2, throughthe field I3 of the voltage regulator motor I4, through wires I5, I6 andI1 to the negative terminal line 0. Closing of the contact I8 of therelay I permits current to flow from positive terminal line E, throughwires 7, 6, 5 and I9, through armature 20, through contact I8, throughthe relay 2|, through the resistance 22, and through wire I1 to thenegative terminal line 0, causing the relay 2| to operate. Current thenflows from the positive terminal line E, through wires 1, 6 and 8,through contact 8 of the relay I, through armature I0, through wires Iand 23, through armature 24 of the relay 2|, through the now closedcontact 25, through resistance 26, through wire 21, through the armatureof the voltage regulator motor I4, through the wire 28, through the nowclosed contact 23 01' the relay 2|, through the armature 30, and throughwires I6 and I! to the negative terminal line 0. Since both the armatureand the field I3 of the voltage regulator motor I4 are now connected topositive and negative, this motor causes the motor driven rheostat W toturn so as to reduce its resistance and bring the regulated voltage atterminal L1 (e) to its proper value. When the voltage at terminal L1 (e)is correct, the contacts of the galvanometer relay G. R. clear,releasing the relay I and the relay 2|, permitting the voltage regulatormotor I4 to stop. When the voltage across terminals E and 0 increases,the galvanometer relay G. R. deflects to the right, causing the relay 3|to operate through a circuit from the negative terminal line 0, throughresistance 2, through the now closed contact 32, through the relay 3 I,through the normally closed contact 33, through wires 34 and l to thepositive terminal line E. The operation of the relay 3| closes thecontact 35, permitting a current to flow from positive terminal line E,through wires 1, 34 and 36, through armature 31 of the relay 3|, throughcontact 35, through wire I2, through field I3 of the voltage regulatormotor I4, and through wires I5, I6 and I1 to negative terminal line 0,thus energizing the field I3 in exactly the same sense as it isenergized by operation of the relay I. However, the relay 2| is notenergized upon operation of the relay 3| (as it is upon operation of therelay I), so that the direction of the current through the armature ofthe voltage regulator motor I4 is reversed, causing the motor to turn inthe opposite direction and to bring the regulated voltage at terminal L1(e) to its proper value. In accomplishing this, the connection from thepositive terminal line E is through the contact 38 of the relay 2I tothe wire 28 connecting to one side of the armature of the motor I4,instead of through contact 25 of the relay 2| to the wire 27 connectingto the other side of the armature of the motor I4.

It should be noted that resistance 26 is provided to reduce the speed ofthe voltage regulator motor I4 and to prevent arcing of the contacts ofthe relay 2I.

It will be noted that the relay 3| operates when the unregulated voltageincreases. Operation of this relay not only causes the contact at 35 tobe closed, as already explained, but at the same time causes the contact39 to open, removing the short-circuit normally existing acrossresistance B. This short-circuited resistance B is provided electricpotential varying over a to compensate for the voltage drop caused bythe sudden connection or the voltage regulator motor |4 upon operationof the relay 3|. For example, it the unregulated voltage increases veryslightly but sufllcient to cause the relay 8| to be operated, theconsequent connection or the voltage regulator motor |4 would increasethe load sufllciently to cause a line drop in voltage equal to orgreater than the initial increase, so that the regulator would beautomatically rebalanced without any adjustment of the motor drivenrheostat W. This would permit the release of the relay 3| and thedisconnecting of the voltage regulator motor l4 which, upon removal orits load, would permit the line voltage to return to its initiallyincreased amount. Consequently, for a slight increase in voltage, theonly action would be a chattering of the relay 3| and the galvanometerG. R. without eflecting any permanent adjusting. The sudden insertion ofthe resistance B by operation of the relay 3| causes the voltage at theterminal of the galvanometer relay connected to the point S to decreasean amount equal to the drop which would be caused by connection of thevoltage regulator motor l4, so that the voltage difference across thegalvanometer relay will be very nearly that which would be obtained ifno load were put on the line by the voltage regulator motor l4.

It will also be noted that if the voltage changes sufllciently the motordriven rheostat W will reach its limit in one direction or another.While the regulator as described is operable to produce a constantregulated voltage fro a source pf de range, it will not regulate overthe entire range, and it is accordingly necessary to provide means forpreventing mechanical injury to the rheostat and its driving mechanism.Limit switches are accordingly provided on the rheostat and arranged insuch a manner that their circuits are opened before the mechanical limitof the rheostat is reached. These limit switches are shown at 40 and 4|for the relays and 3| respectively.

1 Opening of the limit switch 40 when the rheostat W has reached onelimit of its motion disconnects the relay by breaking its energizingcircuit at the contact 4 of the limit switch, causing the voltageregulator motor M to stop. Similarly, opening of the limit switch 4|when the rheostat W has reached the other limit of its motiondisconnects the relay 3| by breaking its energizing circuit at thecontact 33 of the limit switch, likewise causing the voltage regulatormotor |4 to stop. At the same time that the contact 4 of the limitswitch 40 is opened, the contact 42 of the limit switch is closed, thuscompleting a circuit from positive terminal line E, through wires 1, 6and 5, through contact 42, through wire 43, through a trouble bell 44and a trouble lamp 45 in parallel, and through the wire 46 to negativeline terminal 0. Similarly, at the same time that the contact 33 of thelimit switch 4| is opened, the contact .41 of the limit switch isclosed, thus completing a circuit from positive terminal line E, throughwires 1 and 34, through contact 41, through wires 48 and 43, through atrouble bell 44 and a trouble lamp 45 in parallel, and through the wire46 to negative line terminal 0. It will therefore be seen that troublesignals are given when the unregulated line voltage is too high or toolow, i. e., beyond the adjusting range of the regulator, so that propersteps may be taken at once to correct the voltage directly at thesource. A switch 49 is provided in the circuit or the trouble bell 44 sothat the trouble bell may be stopped, but the trouble lamp 45 remainslighted until the trouble has been corrected.

The condensers 50 and 5| shown connected across the relays I and 3|respectively are used to reduce arcing of the contacts of thegalvanometer relay G. R.

The resistance C of the voltage regulator is provided with an adjustabletap to compensate for difierences in resistance of the commerciallywound resistors A and B and also to permit adjustment of the regulatingvoltage due to differences in the voltage produced across each of theglow tubes G and T.

It will, of course, be understood that it the unregulated line voltageacross the terminal lines E and 0 remains constant, and if the loadconnected across the terminals L1 and L2 of the regulated voltagechanges sufiiciently to alter the regulated voltage itself, theregulator arrangement will become unbalanced, and the regulator willoperate to adjust the value of the resistance W so as to return theregulated voltage to its proper value.

It will accordingly be seen that the present invention not only providesa constant voltage across desired terminals despite variations of thevoltage at the source of electric potential, but also despite variationsin the load applied across said terminals.

Referring now to Figure 3, the arrangement here shown is similar to thatshown in Figure 2, but the arrangement of Figure 3 will act to regulatea voltage only of a magnitude equal to the sum of the regulatingvoltages of the glow tubes G and T.

The arrangement of Figure 2, on the other hand, can be employed toproduce a regulated voltage of a magnitude greater than the regulatingvoltage of one glow tube and less than the sum of the regulatingvoltages of two glow tubes. With this arrangement limited changes in therange of the regulated voltage are obtainable in view of the limitedrange of adjustment of the point S of the series of resistances V.

Figure 4 shows another arrangement in accordance with the presentinvention, this arrangement being similar to that of Figure 2, butemploying only a single glow tube T. With this arrangement it ispossible to produce a regulated voltage of any magnitude greater thanthe regulating voltage of the glow tube but less than the unregulatedline voltage. rangement is not quite as sensitive as that of Figure 2,because in Figure 4 the voltage at the point S changes with changes inthe unregulated line voltage, whereas in Figure 2 the voltage at thepoint S remains absolutely constant despite changes in the unregulatedline voltage, as already explained in connection with Figure 2. Limitedchanges in the range of the voltage to be regulated are also obtainablewith the arrangement of Figure 4.

Figure 5 shows an arrangement for obtaining regulated voltages of amagnitude less than the regulating voltage of the glow tube with limitedchanges in the range of the voltage to be regulated, the resistance Rconnected across the glow tubeN being suitably tapped to produce aregulating voltage less than the regulating voltage of the glow tube.

Figure 6 also shows an arrangement for obtaining regulated voltages of amagnitude less However, this arthan the regulating voltage or the glowtube but with wide changes in the range of the voltage to be regulated.As in Figure 5, the resistance R connected across the glow tube N issuitably tapped to produce a regulating voltage less than the regulatingvoltage of the glow tube.

Figure '7 shows an adaptation of the present invention to controllingthe output voltage of an electric generator, so as to maintain itconstant. In Figure '7 the generator is shown at 52 and its outputterminals at 53 and 54. The field 55 of the generator is connected to beenergized from the output of the generator. At the same time a voltageregulating arrangement in accordanc with the present invention isconnected across the output of the generator, and the galvanometer relayof the voltage regulating arrangement is connected to control theresistance of the field 55, so that any change in the magnitude of theoutput voltage of the generator is communicated to the voltageregulating arrangement, which then causes the resistance of the field 55to change in the proper direction for returning the output voltage ofthe generator to its desired constant value, it being understood thatthe value of the output voltage of the generator is determined by thestrength of its field, which in turn is determined by the fieldresistance.

In connection with Figure 7 it will be noted that batteries 56 have beenshown as voltage regulators instead of the voltage regulating neon glowtubes described in connection with the previous figures. It will, ofcourse, be understood that batteries act to maintain a practicallyconstant voltage and therefore may be employed interchangeably with theneon glow tubes or any other type of voltage regulating element, itbeing, of course, apparent that the regulating effect of the presentinvention is based upon the use of a constant voltage regulatingelement.

It should, of course, be further understood that commercially obtainablevoltage regulating elements, such as neon glow tubes, pass only smallcurrents, and will not act to regulate the voltage when connecteddirectly across apparatus drawing a relatively large current.

Figure 8 shows an adaptation of the present invention to controlling thespeed of an electric motor, so as to maintain a constant speed. InFigure 8 the motor is shown at 51, and the motor field at 58, the motorfield being connected to be energized by a source of electric potentialsubject to fluctuations in voltage. There is also shown a relativelysmall output generator 59 connected to be driven by the motor 57, thearrangement constituting a motor-generator set. Across the outputterminals of the generator 59 is connected a. voltage regulatingarrangement in accordance with the present invention, the voltageregulating arrangement being connected to vary the resistance of themotor field 58. Asstuning that the motor has been operating at a desiredconstant speed, and that the voltage regulating arrangement has beenbalanced at the resulting output voltage of the generator, any change inthe voltage energizing the motor, resulting in a change in speed of themotor, will result in a change in the output voltage of the generator,which change will be communicated to the voltage regulating arrangement.The voltage regulating arrangement will then act to vary the resistanceof the field of the motor in such a direction as to return the speed ofthe motor to its desired constant value,

at which time the output voltage of the generator will return to itsdesired constant value, resulting in a return to normal oi! the voltageregulating arrangement.

From the foregoing detailed description of various embodiments andapplications of the present invention, it will be seen that I haveproduced decided improvements in electrical arrangements for obtaining aconstant voltage from a source of electric potential subject tofluctuations in voltage, and that I have accomplished the variousobjects set out at the beginning of this specification. understood fromthe foregoing description that my invention is not only capable of wideapplication, but that it can be carried out in various styles ofexecution, and Y accordingly do not wish my invention to be limited saveas defined in the appended claims.

1. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electric potential subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement having aconstant voltage element as one arm of the bridge, a variableresistance, means to connect the bridge and said variable resistance inseries with each other and with said source, means to vary the value ofsaid resistance, and means to control the resistance varying means uponunbalance of the bridge following a voltage variation for causing achange in the value of the resistance, whereby to reestablish thebalance of the bridge, the desired regulated load voltage being obtainedfrom at least one arm of the bridge.

2. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electric potential subjcct to fluctuations involtage, which comprises a Wheatstone bridge arrangement having aconstant voltage element as one arm of the bridge, a variable resistanceforming another arm of the bridge, means to connect the bridge so as tobe subject to the voltage capable of fluctuating, means to vary thevalue of said resistance, and means to control the resistance varyingmeans upon unbalance of the bridge following a voltage variation forcausing a change in the value v of the resistance, whereby toreestablish the balance of the bridge, the desired regulated loadvoltage being obtained from that arm of the bridge which is in serieswith said variable resistance.

3. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electric potential subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement having aconstant voltage element as one arm of the bridge, a resistance formingone parallel side of the bridge and having means associated therewithfor varying the proportion of resistance in the two arms forming saidparallel side of the bridge, means to connect the bridge so as to besubject to the voltage capable of fluctuating, and means to control theresistance varying means upon unbalance of the bridge following avoltage variation for causing a change in proportion of the resistancein said two arms of the bridge, whereby to reestablish the balance ofthe bridge, the desired regulated voltage being obtained from It willalso be that portion of the resistance which directly parallels theconstant voltage element.

4. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electric potential sub- Ject to fluctuationsin voltage, which comprises a Wheatstone bridge arrangement having aconstant voltage element as one arm of the bridge,

a variable resistance, means to connect the bridge and said variableresistance in series with each other and with said source, means to varythe value of said resistance, and means to control the resistancevarying means upon unbalance of the bridge following a voltage variationfor causing a change in the value of the resistance, whereby toreestablish the balance of the bridge, the desired regulated loadvoltage being maintained across and obtainable from the bridge.

5. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electric potential subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement having constantvoltage elements in diagonally opposite parallel arms thereof, avariable resistance, means to connect the bridge and said variableresistance in series with each other and with said source, means to varythe value of said resistance, and means to control the resistancevarying means upon unbalance of the bridge following a voltage variationfor causing a change in the value of the resistance, whereby toreestablish the balance of the bridge, the desired regulated voltagebeing maintained across and obtainable from the bridge.

6. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electric potential subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement having aconstant voltage element as one arm of the bridge, a variableresistance, means to connect the bridge and said variable resistance inseries with each other and with said source, means to vary the value ofsaid resistance comprising a two-way driving mechanism, and a pair ofelectrical contacts controlled by the bridge galvanometer, one of whichcontacts is controlled by the galvanometer upon unbalance of the bridgefollowing a voltage change in one direction and the other of which iscontrolled by the galvanometer upon unbalance of the bridge following avoltage change in the other direction, one of said contacts serving tocontrol the driving mechanism to cause it to vary the value of saidresistance in one direction and the other of said contacts serving tocontrol the driving mechanism to cause it to vary the value of saidresistance in the opposite direction, whereby to reestablish the balanceof the bridge, the desired regulated voltage being obtained from atleast one arm of the bridge.

7. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electric potential sublect to fluctuations involtage, which comprises a Wheatstone bridge arrangement having aconstant voltage element as one arm of the bridge, a variableresistance, means to connect the bridge and said variable resistance inseries with each other and with said source, means to vary the value ofsaid resistance comprising a two-direction electric motor having theusual field and armature, a relay having contacts adapted to effectenergization of the motor armature in one sense when the relay isdeenergized and to effect energization of the motor armature in theopposite sense when the relay is energized; a second relay having a pairof contacts, one of which is adapted to effect energization of the motorfield in one certain sense, and the other of which is adapted to effectenergization of the first named relay; a third relay having a contactadapted to effect energization of the motor field in the same certainsense as before mentioned; a pair of electrical contacts controlled bythe bridge galvanometer, one of which contacts is controlled by thegalvanometer upon unbalance of the bridge following a voltage change inone direction and the other of which is controlled by the galvanometerupon unbalance of the bridge following a voltage change in the otherdirection; one of said contacts serving to effect energization of thesecond named relay to cause it to effect operation of the motor in onedirection to effect variation in the value of said resistance in onedirection, and the other of said contacts serving to effect energizationof the third named relay to cause it to effect operation of the motor inthe opposite direction to eifect variation in the value of saidresistance in the opposite direction, whereby to reestablish the balanceof the bridge; the

desired regulated voltage being obtained from at least one arm of thebridge.

:3. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electric potential subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement having aconstant voltage element as one arm of the bridge, a variableresistance, means to connect the bridge and said variable resistance inseries with each other and with said source, means to vary the value ofsaid resistance comprising a two-way driving mechanism, a. relay havingcontacts adapted to effect operation of the driving mechanism in onedirection to cause it to vary the value of said resistance in onedirection, a second relay adapted to effect operation of the driv ingmechanism in the other direction to cause it to vary the value of saidresistance in the opposite direction, means to effect deenergization ofthe first named relay and of the driving mechanism when said resistancereaches the limit of its adjustment in one direction; means to effectdeenergization of the second named relay and of the driving mechanismwhen said resistance reaches the limit of its adjustment in the oppositedirection; and a pair of electrical contacts controlled by the bridgegalvanometer, one of which contacts is controlled by the galvanometerupon unbalance of the bridge following a voltage change in one directionand the other of which is controlled by the galvanometer upon unbalanceof the bridge following a voltage change in the other direction; one ofsaid contacts serving to control the first named relay to cause it toeffect operation of the driving mechanism to effect variation in thevalue of said resistance in one direction, and the other of saidcontacts serving to control the second named relay to cause it to effectoperation of the driving mechanism to effect variation in the value ofsaid resistance in the opposite direction, whereby to reestablish thebalance of the bridge; the desired regulated voltage being obtained fromat least one arm of the bridge.

9. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electric potential subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement having aconstant voltage element as one arm of the bridge, a variableresistance, means to connect the bridge and said variable resistance inseries with each other and with said source, means to vary the value ofsaid resistance comprising a twoway driving mechanism, a relay havingcontacts adapted to effect operation of the driving mechanism in onedirection to cause it to vary the value of said resistance in onedirection, a second relay adapted to efiect operation of the drivingmechanism in the other direction to cause it to vary the value of saidresistance in the opposite direction, a limit switch having a normal- 1yclosed contact in the energizing circuit of the first named relay, asecond limit switch having a normally closed contact in the energizingcircult of the second relay; means to effect opening of the normallyclosed contact of the first named limit switch when said resistancereaches the limit of its adjustment in one direction, so as to effectdeenergization of the first named relay and of the driving mechanism;means to effect opening of the normally closed contact of the secondnamed limit switch when said resistance reaches the limit of itsadjustment in the opposite direction, so as to effect deenergization ofthe second named relay and of the driving mechanism; and a pair ofelectrical contacts controlled by the bridge galvanometer, one of whichcontacts is controlled by the galvanometer upon unbalance of the bridgefollowing a voltage change in one direction and the other of which iscontrolled by the galvanometer upon unbal-. ance of the bridge followinga voltage change in the other direction; one of said contacts serving tocontrol the first named relay to cause it to effect operation of thedriving mechanism to efiect variation in the value of said resistance inone direction, and the other of said contacts serving to control thesecond named relay to cause it to efi'ect operation of the drivingmechanism to efiect variation in the value of said resistance in theopposite direction, whereby to reestablish the balance of the bridge;the desired regulated voltage being obtained from at least one arm ofthe bridge.

10. An electrical arrangement for maintaining at a. regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electrical potential subject to fluctuationsin voltage, which comprises a Wheatstone bridge arrangement having aconstant voltage element as one arm thereof and a constant voltageelement paralleling the diagonally opposite arm and a portion of thedirectly opposite arm, a variable resistance, means to connect thebridge and said variable resistance in series with each other and withsaid source, means to vary the value of said resistance comprising atwo-way driving mechanism, a relay having contacts adapted to efiectoperation of the driving mechanism in one direction to cause it to varythe value of said resistance in one direction, a second relay adapted toeffect operation of the driving mechanism in the other direction tocause it to vary the value of said resistance in the opposite direction;a pair oi electrical contacts controlled by the bridge galvanometer, oneof which contacts is controlled by the galvanometer upon unbalance ofthe bridge following a voltage change in one direction and the other ofwhich is controlled by the galvanometer upon unbalance oi the bridgefollowing a voltage change in the other direction, one of said contactsserving to control the first named relay to cause it to effect operationof the driving mechanism to effectvariation in the value of saidresistance in one'direction, and the other of said contacts serving tocontrol the second named relay to cause it to effect operation of thedriving mechanism to effect variation in the value of said resistance inthe opposite direction, whereby to reestablish the balance of thebridge, the desired regulated voltage being maintained across andobtainable from the bridge; and means to prevent undesired balancing ofthe bridge upon an increase in voltage of such a magnitude that it wouldbe balanced by reason of an equivalent decrease in voltage occasioned byconnection of the driving mechanism to the voltage source, comprisingmeans normally short-circuiting a portion of the aforesaid arm directlyparalleling the first named constant voltage element, comprising anormally closed contact 01' the second named relay, the short-circuitbeing removed upon operation of the second named relay when it acts toeflect operation of the driving mechanism to effect variation in thevalue of the first named resistance, upon an increase in voltage asbefore mentioned, to restore the regulated voltage to its proper value.

11. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which issupplied from a source of electric potential subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement having aconstant voltage element as one arm thereof and a constant voltageelement paralleling the diagonally opposite arm and a portion of thedirectly opposite arm, a variable resistance, means to connect thebridge and said variable resistance in series with each other and withsaid source, means to vary the value of said resistance, means tocontrol the resistance varying means upon unbalance of the bridgefollowing a voltage variation for causing a change in the value of theresistance, whereby to reestablish the balance of the bridge, thedesired regulated voltage being maintained across and obtainable fromthe bridge; and means to prevent undesired balancing of the bridge uponan increase in voltage of such a magnitude that it would be balanced byreason of an equivalent decrease in voltage occasioned by connection ofthe resistance varying means to the voltage source, comprising meansnormally short-circuiting a portion of the aforesaid arm directlyparalleling the first named constant voltage element, the short-circuitbeing removed upon operation of the resistance varying means to effectvariation in the value of the first named resistance, upon an increasein voltage as before mentioned, to restore the regulated volt age to itsproper value.

12. An electrical arrangement for maintainting at a regulated value thevoltage across a load which may be subject to variation and which isenergized from a source of electric potential subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement, means toconnect the bridge so as to be directly subjected to at I least aportion of the voltage subject to fluctuations, means comprising aconstant voltage element for maintaining a constant voltage drop in onearm of the bridge, said bridge being initially balanced to give adesired regulated voltage drop in at least one arm of the bridge, andmeans controlled by unbalance of the bridge to reestablish the balanceof the bridge and the desired regulated voltage.

13. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which isenergized from a source of electric potential subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement, a variableresistance, means to connect the bridge and said variable resistance inseries with each other and with said source, means comprising a constantvoltage element for maintaining a constant voltage drop in one arm ofthe bridge, said bridge being initially balanced so as to give a desiredvoltage drop in at least one arm of the bridge, and means controlled byunbalance oi! the bridge to vary the value oi! said variable resistancein consonance with variations in voltage of the source of voltage toreestablish the balance 01 the bridge and the desired regulated voltage.

14. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which isenergized from a source of electric potential subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement, means toconnect the bridge so as to be subjected to at least a portion of thevoltage subject to fluctuations, means comprising a constant voltageelement for maintaining a constant voltage drop in one arm of thebridge, said bridge being initially balanced to give a desired regulatedvoltage drop in at least one arm of the bridge, and means controlled byunbalance of the bridge to vary the resistance of at least one arm ofthe bridge in consonance with variations in voltage of the source 0!voltage to reestablish the balance of the bridge and the desiredregulated voltage.

15. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which isenergized from a source of electrical potential subject to fluctuationsin voltage, which comprises a Wheatstone bridge arrangement, a variableresistance, means to connect the bridge and said variable resistance inseries with each other and with said source, means comprising a constantvoltage element for maintaining a constant voltage drop in one arm ofthe bridge, said bridge being initially balanced to give the desiredregulated voltage drop in at least one arm of the bridge, and meanscontrolled by unbalance of the bridge to vary the value of said variableresistance in consonance with variations in voltage of the source ofvoltage to reestablish the balance of the bridge and the desiredregulated voltage, said last named means comprising a two-way drivingmechanism, and a pair of electrical contacts controlled by the bridgegalvanometer, one of which contacts is controlled by the galvanometerupon unbalance of the bridge following a voltage change in one directionand the other of which is controlled by the galvanometer upon unbalanceof the bridge following a, voltage change in the other direction, one ofsaid contacts serving to control the driving mechanism to'cause it tovary the value of said variable resistance in one direction and theother of said contacts serving to control the driving mechanism to causeit to vary the value of said variable resistance in the oppositedirection.

16. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which isenergized from a source of electric potential-subject to fluctuations involtage, which comprises a Wheatstone bridge arrangement, means toconnect the bridge so as to be subjected to at least a portion of thevoltage subject to fluctuations, means comprising a constant voltageelement for maintaining a constant voltage drop in one arm of thebridge, said bridge being initially balanced to give a desired regulatedvoltage drop in at least one arm of the bridge, and means controlled byunbalance of the bridge to vary the resistance of at least one arm ofthe bridge in consonance with variations in voltage of the source ofvoltage to reestablish the balance of the bridge and the desiredregulated voltage, said last named means comprising a two-way drivingmechanism, and a pair of electrical contacts controlled by the bridgegalvanometer, one of which contacts is controlled by the galvanometerupon unbalance of the bridge following a voltage change in one directionand the other of which is controlled by the galvanometer upon unbalanceof the bridge following a voltage change in the other direction, one orsaig contacts serving to control the driving mechanism to cause it tovary the value of said resistance in one direction and the other of saidcontacts serving to control the driving mechanism to cause it to varythe value of said resist ance in the opposite direction.

17. In the art of maintaining at a regulated value the voltage acrossaload, which may be subject to variation and which is energized from asource of electric potential subject to fluctuations in voltage, thesteps consisting in connecting a Wheatstone bridge arrangement so as tobe directly subjected to at least a portion of the voltage subject tofluctuations, maintaining a constant voltage drop in one arm of thebridge despite the fluctuations in voltage to which the bridge issubjected, initially balancing the bridge to give a desired regulatedvoltage drop in at least one arm of the bridge, from which the desiredload voltage is derived, and utilizing the unbalance of the bridge upona variation in voltage to which the bridge is subjected to control meansto reestablish the balance of the bridge, whereby to reestablish thedesired regulated load voltage.

18. An electrical arrangement for maintaining at a regulated value thevoltage across a load which may be subject to variation and which isenergized from a source of electric potential subject to fluctuations involtage, which comprises voltage changing means connected so as tocontrol the voltage across the load, an electrical device connected soas to be responsive to changes in the voltage across the load, saidelectrical device being initially balanced when the load voltage is atits desired regulated value, means controlled by the electrical deviceupon increases and decreases of the voltage across the load to actuatethe voltage changing means to reestablish the balance of the electricaldevice and the desired regulated load voltage, and means to preventundesired balancing of the electrical device upon an increase in voltageof such magnitude that it would be balanced by reason of an equivalentdecrease in voltage occasioned by actuation of the means controlled bythe electrical device, comprising means operable upon actuation of themeans controlled the electrical device to cause a rise in voltage acrossthe elec trlcal device substantially numerically equal to drop whichwould otherwise occur upon actuation of the means controlled by theelectrical device, whereby to restore the unbalanced condition of theelectrical device occurring upon an increase in voltage to therebyenable the desired balanced condition to be effected by the intended 0eration of the means controlled by the electricol device.

19. An electrical arrangement for maiutaining at a regulated value thevoltage across a load which may be subject to variation and which isenergized from a source of electric potential subject to fluctuations involtage, which cornprises a Wheatstone bridge arrangement, means toconnect the blclge so as to be directly subjected to at least a portionof the voltage subject to fluctuations, means comprising a constantvoltage element for maintaining a constant voltage drop in one arm ofthe bridge, said bridge being initially balanced to give a desiredregulated voltage drop in at least one arm of the bridge, meanscontrolled by the bridge galvanorneter upon unbalance of the bridge toreestablish the balance of the bridge and the desired regulated voltage,and means to prevent undesired balancing of the bridge upon an increasein voltage of such magnitude that it Would be balanced by reason of anequivalent decrease in voltage occasioned by connection of the balancereestablishing means to the voltage source, comprising means operableupon connection of the balance reestablishing' means to the voltagesource to vary the resistance of at least one arm of the Wheatstonebridge to cause a rise in volt age across the bridge galvanometersubstantially numerically equal to the drop Which would otherwise occurupon connection of the balance reestablishing means to the voltagesource, whereby to restore the unbalanced condition occurring upon anincrease in voltage to thereby enable the desired balanced condition tobe effected by the intended operation of the balance reestablishingmeans.

HARRY CAMPBELL GRANT, J a.

